Upgrade Analysis for CUCM 8.5(1) to 8.6(2a), 9.0(1), or 9.1(1a)

Has anyone done any analysis like this that they would be willing to share? We are trying to determine upgrade complexity among these 3 options, considering licensing, any upgrade caveats, and potential user-facing changes. We'll be performing the potential upgrade on UCS-B platforms, and essentially, we need to choose one of these options to maintain UCCE compatibility, while keeping disruption to a minimum.

I don't have any experience with UCCE, but 9.0 is a dead release, it has been replaced with 9.1.1a in all orders, etc. You should not be using because of the licensing issues. No matter how you slice it any of those upgrades is a refresh so it will require that the upgrade occur during a maintenance window as the server will go down during the upgrade process. If you do 8.6, no licenses to deal with. 9.1 does however come with some nice new features like native queuing for hunt groups.

Has anyone done any analysis like this that they would be willing to share? We are trying to determine upgrade complexity among these 3 options, considering licensing, any upgrade caveats, and potential user-facing changes. We'll be performing the potential upgrade on UCS-B platforms, and essentially, we need to choose one of these options to maintain UCCE compatibility, while keeping disruption to a minimum.

I've done a upgrade from 8.5.1 to 9.1.1a with no issues. Licensing is different as you know, but basically installed the refresh_upgrade cop file then did the 9.1.1 upgrade file and booted on new version and went fine. VM's are on UCS B as well. Separate ELM server. Upgrade from 8.5.1 to 9.1.1 did not take much longer than a normal 8.5 SU took. For our setup, that is about 1.5 hr to 2 hrs for publisher install and 1 hour for each subscriber. The switch version for each server took 20-30 minutes to complete per server.